The present invention relates to vehicle electronic systems, and more specifically, to electronics for use in diagnostics, protection, and isolation of electronic devices connected to a data communication bus in a vehicle.
Present-day vehicles often include electronic control modules or other electronically-controlled devices that exchange digital data information via a data communication bus implemented in the vehicle. The Society of Automotive Engineers (SAE) has established a number of protocols to standardize data communication in vehicle applications. For example, SAE J1708 is a commonly used specification for implementing the physical layer of a data communication bus in a vehicle. Data communicated on a J1708 data communication bus is typically transmitted in accordance with SAE J1587 data transmission protocol. Another commonly used specification for data transmission in a vehicle is SAE J1939. While these specifications are directed primarily to data communication in heavy duty vehicles (e.g., tractor-trailers), the specifications may also be applied to light-duty vehicle applications.
FIG. 1 illustrates a basic configuration of a data communication bus 10 implemented in accordance with SAE J1708. The data communication bus 10 is a two-wire bus to which a plurality of electronic devices is connected. For example, FIG. 1 depicts a dashboard electronic control module 12 and an engine electronic control module 14 connected to the data communication bus 10. FIG. 1 also illustrates other electronic devices connected to the data communication bus 10, such as an anti-lock brake system 16 and a trailer electronic control module 18. A bus interface port 20 connected to the data communication bus 10 permits an external diagnostics/programming device to access the data communication bus 10 to monitor and/or program the electronic devices in the vehicle (e.g., the dashboard control module 12, the engine control module 14, the anti-lock brake system 16, and the trailer electronic control module 18).
In vehicle production, electronic devices are typically installed in a vehicle and connected to the data communication bus 10 during the vehicle assembly process. The electronic devices are then programmed via the data communication bus 10 at a single location near the final assembly stage. Furthermore, when the vehicle is being serviced at a later date, it is customary to program replacement electronic devices via the data communication bus 10 after the replacement electronic devices are installed in the vehicle. Electronic devices that are added to the vehicle at a later date are also typically programmed via the data communication bus 10.
While programming electronic devices via a common data communication bus is believed to reduce the amount of hardware required and simplify the installation process, it can have unintended effects. For instance, programming codes intended to program one electronic device on the bus may inadvertently affect the programming of another device on the bus. In other circumstances, the programming codes intended to program a given device may conflict with information being broadcast on the bus by other devices. Since the programming codes for programming an electronic device are often proprietary to the manufacturer of the device and typically are not published, it is not feasible to administratively coordinate the multitude of manufacturers to avoid data interference on the bus. This problem becomes even more acute as the number of electronic devices added to the vehicle increases. A need, therefore, exists for methods and apparatus that can isolate electronic devices on the bus during programming to avoid cross-interference of the programming codes.
Furthermore, if an electronic device connected to the data communication bus 10 develops a fault or is improperly installed, the electronic device may cause system-wide bus disturbances. Such bus disturbances, or abnormalities, may include the transmission of invalid characters, excess packet length, babbling (i.e., transmission of excessive data that is valid but otherwise prevents other devices from transmitting), corrupt packets (e.g., packets with invalid checksums), or faulty hardware conditions that prevent data transmission (e.g., a shorted bus, or a reverse polarity on the bus). The result of these bus disturbances may range from a minor annoyance to creating an unsafe driving condition for the vehicle. Troubleshooting to identify an offending electronic device causing a bus disturbance is a costly and time-consuming exercise, particularly as the number of electronic devices being connected to the data communication bus increases. A need, therefore, exists for methods and apparatus that can isolate electronic devices from a data communication bus during diagnostics to identify electronic devices that are causing problems on the bus. The foregoing needs, and other shortcomings in the prior art, such as a need for real-time bus monitoring and logging of bus disturbances, are addressed by the present invention.
The present invention provides apparatus and methods for use in programming and diagnostics of electronic devices in a vehicle. The electronic devices communicate via a data communication bus in the vehicle. In one exemplary embodiment of the invention, a system is provided with a connector jack, a shorting plug, and an electronics module. The connector jack has a plurality of electrical connection sites that are configured for electrical connection to the electronic devices in the vehicle. The shorting plug is configured to removably engage the connector jack. When the shorting plug is engaged with the connector jack, the shorting plug electrically interconnects the plurality of electrical connection sites to form the data communication bus. The electronics module is configured to removably engage the connector jack in place of the shorting plug. The electronics module includes a plurality of switching units that connect to the plurality of electrical connection sites in the connector jack when the electronics module is engaged with the connector jack.
In accordance with the present invention, when each switching unit in the electronics module is set in a closed state, the electronic devices in the vehicle are interconnected in the electronics module to form the data communication bus. Preferably, each switching unit in the electronics module is operable separately from the other switching units. One or more of the switching units may be selectively set in an open state to electrically disconnect an electronic device from the data communication bus.
A method according to the present invention for use in programming electronic devices in a vehicle includes connecting the electronic devices to the data communication bus via switching units that are set in a closed state. An external programming device connected to the data communication bus transmits programming codes via the data communication bus to an electronic device in the vehicle that is to be programmed. In accordance with the present invention, the other electronic devices in the vehicle that are not to be programmed are electrically disconnected from the data communication bus by setting in an open state the switching units that connect the other electronic devices to the data communication bus. In this manner, only the electronic device intended to be programmed is connected to the data communication bus during programming. After the programming is completed, the other electronic devices that were electrically disconnected from the data communication bus may be reconnected by setting all of the switching units back in a closed state. The external programming device may also be removed from the data communication bus.
A method according to the present invention for use in diagnostics of vehicle electronic devices includes connecting the electronic devices to a data communication bus via switching units set in a closed state. A processing unit monitors data communicated by the electronic devices on the data communication bus for abnormalities. If an abnormality in the data is detected, the method includes setting one or more of the switching units in an open state to electrically disconnect from the data communication bus one or more of the electronic devices. The electronic devices may be disconnected from the data communication bus in a sequence until the abnormality is no longer detected on the data communication bus. In this manner, the electronic device that is causing the abnormality may be identified.
An electronics module constructed in accordance with the present invention includes a module connector configured to engage a connector jack in the vehicle having a plurality of electrical connection sites. The electrical connection sites are connected to the electronic devices in the vehicle. A set of switches in the electronics module includes a plurality of switching units that are connected to the module connector. When the module connector is engaged with the connector jack and the switching units in the electronics module are set in a closed state, the electronics module interconnects the electronic devices in the vehicle to form the data communication bus.
A processing unit in the electronics module is configured to selectively set each of the switching units in the set of switches in an open or closed state. Accordingly, the processing unit may direct one or more of the switching units to be set in an open state, and thus electrically disconnect an electronic device in the vehicle from the data communication bus. The processing unit may selectively disconnect an electronic device based on instructions received from a memory or a user input in the electronics module. The processor may also be configured to monitor data communicated on the data communication bus and selectively set one or more of the switching units in an open or closed state based on data communicated on the data communication bus. If an abnormality in the data communicated on the data communication bus is detected, the electronics module may electrically disconnect one or more of the electronic devices from the data communication bus to identify the electronic device that is causing the abnormality.
The electronics module may be embodied in a service-type apparatus that is connected to the data bus on a temporary basis, or it may be installed in a vehicle on a more permanent basis. In either case, the electronics module controls a set of switching units connecting the vehicle""s electronic devices to the data communication bus, as previously described. The electronics module may also include an output device for reporting information to a user, such as information related to an abnormality detected on the data communication bus.